The spin correlation in a ferromagnet with random anisotropy

A computer simulation technique has been used to study the static spin correlation in a ferromagnet with random magnetic anisotropy. An effective anisotropy constant which enables us to express the spin correlation by the domain wall equation was calculated for various values of single-ion anisotropy constant. Allowing the spin tunnelling or not makes a significant difference in the high anisotropy region. The energy of a relaxed domain wall was calculated and it was shown that the domain wall energy approached to zero in the Ising limit, suggesting the instability of the ferromagnetic remanent state. The ground state can be obtained by creating reverse domains in the ferromagnetic state, and should be classified as the spin-glass state. The temperature dependence of the coercivity of the amorphous magnet was explained by the theory developed for highly anisotropic crystalline magnets.